For an in-cylinder direct injection engine, a technique is known which increases an exhaust temperature by injecting fuel in an expansion stroke in order to activate an exhaust gas purifying catalyst early in a warm-up process from a cold start.
In a situation where an exhaust gas purifying catalyst needs to be activated early, the exhaust gas purifying catalyst cannot exhibit a sufficient purifying function. Thus, it is also necessary to reduce the amount of emissions such as HC and NOx from an engine. Particularly, since fuel having collided with a cylinder wall surface and a piston crown surface (hereinafter, also referred to as wall surfaces and the like) are likely to directly adhere to the wall surfaces and the like and be liquefied in a warm-up process from a cold start, the amount of unburned HC emissions tends to increase.
Accordingly, a technique for performing spark ignition before the tip of fuel spray reaches the wall surfaces and the like by injecting fuel in an expansion stroke in order to combine early activation of the exhaust gas purifying catalyst and a reduction of emission components such as HC is disclosed in JP2006-52687A.